1. Field of the Invention
The present invention relates to a vibration-detecting sensor and a method of detecting vibration. The vibration-detecting sensor is mounted to a vibrating object, and detects vibration generated by the vibrating object.
2. Description of Related Art
A knock sensor, i.e., vibration sensor, for detecting engine knock vibration is mounted to a cylinder block of a vehicle engine, for example.
JP-A-9-126876 discloses a vibration sensor including a base, a silicon semiconductor substrate, a vibrating portion and a weight. The substrate is disposed on the base, and the vibrating portion is integrated with the substrate. The vibrating portion is displaced in accordance with the knock vibration. The weight is arranged on the vibrating portion such that the vibrating portion resonates with the knock vibration.
The vibration sensor detects the knock vibration due to the resonance of the vibrating portion. Therefore, the vibrating portion and the weight are set such that a natural frequency of the vibrating portion corresponds to a frequency of the knock vibration.
However, because the weight is required to be set in accordance with an engine type, many kinds of the weights are needed to correspond to many kinds of the engines. Therefore, productivity and general versatility of the vibration sensor are low.
Further, the vibration sensor detects only vibration in a narrow range of frequency set in accordance with the engine. Therefore, non-knock vibration generated by other factors except the knock vibration is difficult to be detected, and the vibration sensor is difficult to detect the knock vibration separately from general noise.